Packaging machine with several heater elements

ABSTRACT

The disclosure relates to a packaging machine and a method, in particular for an intermittently operating deep-draw packaging machine, which has at least one heating surface with a plurality of heater elements, which can be individually controlled by a controller in order to heat a film to different temperature levels. The heater elements are formed as thick-film heater elements

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims foreign priority benefits under 35 U.S.C.§119(a)-(d) to German patent application number DE 102009041563.7, filedSep. 15, 2009, which is incorporated by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates to a packaging machine and method forheating of a film to be deformed.

BACKGROUND

From the state of the art, deep-draw packaging machines are known whichhave a moulding station in which a film is heated by means of a heatingplate such that it can then be formed into a cavity in the lower part ofthe mould tool. The process must take place very quickly, because on onehand due to the generally cooler compressed air, which is initiallypresent over the complete surface of the upper part of the mould tool,the film is cooled, and on the other hand in the upper regions of theside walls and in the region of the bottom of the mould cavity in thelower part of the mould tool the film can become so cold during themoulding process that subsequent deformation of the film leads to anundesirable or too thin wall thickness, or adequate forming in the wholeregion of the cavity is no longer possible, because the film has cooledbelow the temperature required for plastic deformation.

Above all, with large deep-drawing depths and small radii in the regionof the cavity bottom, there is a great risk that the wall thickness ofthe film after deformation is too different and these cavities must nolonger be used for quality reasons and have to be extracted.

In order to be able to individually heat the film before the mouldingprocess, zone heaters can be employed in which the heating plate hasbeen manufactured according to the cavity shape so that differentregions of the film are heated differently in order to obtain a uniformwall thickness of the film in the subsequent process. This embodiment isconstructively very elaborate and extremely inflexible, because it islinked to the package shape.

From JP 55095519, U.S. Pat. No. 5,280,434, DE 102006045327 and GB1405753 heating devices are known with which a heating surface has alarge number of heater elements which can be controlled individually tobe able to generate different temperatures on the individual heaterelements. The known embodiments are not suitable for also fitting to amoulding stamp nor to moulding surfaces of a lower part of a mould toolsuch as side walls and bottom surface in order to generate differenttemperatures in these regions and thus to be able to positivelyinfluence the moulding process.

In the application DE 102009030508.4, which has not yet been published,a further alternative technique is described. Here, in a film to bedeformed, a spatially inhomogeneous temperature distribution is producedso that the film is optimally prepared according to the requirements ofthe moulding process. This is preferably however realised by a simplecontinuously heated heating plate and special properties of the film.

A further disadvantage of the state of the art is a continuously heatedheating plate with a simultaneously cooled upper part of the mould tool.In order to be able to apply the required heat energy to the film formoulding the film and simultaneously to be able to maintain the generalprocessing times in the deep-draw packaging machine short for a highmachine capacity, the heating plate is continuously at the necessarytemperature, which is transferred to the film at the moment of feedingor heating the film for an appropriate time in the moulding station.These high temperatures of over 100° C. require cooling of the upperpart of the mould tool above the heating plate to provide protectionagainst injuring the operating personnel through burning by touching therelatively freely accessible upper part of the mould tool.

This high energy storage in the heating plate also has disadvantages inthe heating up phase, for example after a tool change, and in a waitingperiod before renewed setting up in the region of the moulding stationdue to the necessity of the heating plate having to cool down.

From DE 102005043026 a reference is known from the field of householdappliances to a possible use of a thick-film heater for heating upwater. Here, the economical manufacture and the low space requirementshould offer advantages.

SUMMARY

An object of the present disclosure is to provide a device which issuitable for heating a film individually with different temperaturelevels taking into account in this respect the energy consumptionrequired for the moulding process and eliminating the disadvantages ofthe state of the art.

For the purpose of the disclosure, “thick-film heating” is taken to meanheating in which the heater elements (without substrate or carrier) havea thickness of at least 1 μm. The term “heater element” is usedsynonymously with “heating circuit”.

The embodiment of the heating surface according to this disclosure hasthe advantage that due to the low proportion of material the thick-filmheaters can be heated quickly to the required temperature and are ableto cool down to the ambient temperature just as quickly, because thereis no accumulation of heat. In conjunction with a controller thisfacilitates a temporally limited switch-on period of the thick-filmheater elements during which the film is to be heated, and thus lowenergy consumption.

Due to a uniform distribution of a plurality of thick-film heaters, ahigh flexibility with regard to different package shapes is alsoproduced.

The plurality of heater elements, preferably distributed on the heatingsurface uniformly or in matrix form, can heat a film individuallythrough the individual control of the heater elements such thatdifferent regions or areas of the film can be heated to various levels.This leads to different temperature levels, which can be producedappropriately to the subsequent moulding process in order to obtain thedesired wall thicknesses and deformations of the moulded cavity duringor after the moulding process.

Above all with moulding processes with large deep-drawing depths, smallradii and thin films the packaging machine according to the inventionpresents a solution, which offers a more favourable solution in terms ofenergy than the state of the art and which ensures increased processreliability and thus attainment of the quality of the packaging cavity.

For the usual necessity of being able to produce different cavity shapeson one and the same deep-draw packaging machine the heating deviceaccording to the invention is found to be an economical solution,because no elaborate components have to be made available specially forthe moulding process nor set up during a change of product, and becausethe individually produced temperature levels, which are necessary forthe film, can be saved in the controller and recalled. This can lead tothe shortest changeover times. Also changes to the different temperaturelevels are possible via the controller in order to be able to matchvarying boundary conditions in the moulding process. These boundaryconditions may be, for example, shorter operating cycles or varying filmthicknesses.

The thick-film technology facilitates integration of a plurality ofheater elements in a common layer, which can be fitted on a carrierplate and thus be formed as a heating plate. Preferably, a flatarrangement of this nature can be fitted in an upper part of the mouldtool or can preheat the films as a preheater above and/or below the filmbefore the moulding station if the time available in the mouldingstation is not sufficient.

It is conceivable to fit the heater elements individually and to realisethem individually or collectively connected to the controller. On adisplay assigned to the controller the temperature levels can beindividually entered, saved and/or specified and fed into the packagingmachine from outside in dependence of the heater elements present.

During the moulding process, with the initial contact of the film with astamp or the surfaces of the moulding cavity in the lower part of themould tool, rapid cooling of the film may occur in these partialregions. The consequence of this may be that the film in these partialregions can no longer extend sufficiently and the wall thickness of thefilm in the remaining regions reduces excessively. This undesiredbehaviour during the moulding process can be countered with thepackaging machine according to the invention, if in addition oralternatively heating surfaces are fitted at least partially on thestamp or on the walls and/or bottom of the moulding cavity. Thus, thefilm can be maintained deformable also in these partial regions througha specific temperature level for as long as is necessary for themoulding process.

The embodiment as a thick-film heater offers the advantage of coolingthe heater elements in the shortest time through cooling in the regionof the moulding cavity, for example by means of cooling water channels,such that the heater elements assume the temperature of the cooledmoulding cavity or of the lower part of the mould tool and thus thishardly delays the cooling process of the deep-drawn film.

The use of the packaging machine according to the invention isparticularly practicable in an intermittently operating deep-drawpackaging machine, because here the time for an operational cycle, alsoof the sealing station in the manufacture of packaging under a modifiedatmosphere, is influenced and in this respect an unwanted dwell time ofthe film in the moulding station and heating device can occur. Thedescribed problem can be avoided by the thick-film heaters which areswitched off during this period.

The packaging machine according to the invention has a further positiveeffect during the use and processing of plastic films, which are mostlymulti-layered and in line with their properties should therefore beheated very individually for the moulding process in order to be able toobtain the desired results.

The methodical sequence according to the invention with anintermittently operating deep-draw packaging machine with at least oneheating surface, which has a plurality of preferably uniformlydistributed thick-film heaters, whereby a controller can individuallycontrol these thick-film heaters, primarily has advantages when heatinga film to be deformed to different temperature levels.

At the start of an operational cycle the moulding station of thedeep-draw packaging machine is fed with the film in the form of astrip-shaped material by means of a feed system via gripper chainsarranged on both sides. Then the moulding station is closed and a closedchamber is created. The controller can meanwhile, or also only after theclosure of the moulding station, control and heat up the heater elementswhich are realised as thick-film heater elements. This control can beimplemented according to a program saved in the memory of the controlleror can occur through entries fed into the controller by the operatingpersonnel.

In order to introduce the heat energy into the film, the film ispreferably drawn onto the heater elements by a negative pressure in theupper part of the mould tool, so that the film is located uniformly onthe heater elements. The film heats up accordingly and the desiredindividual temperature levels arise within the film.

The controller switches off the heater elements once the film mouldingprocess starts and the film is deformed into the lower part of the mouldtool by means of compressed air in the upper part of the mould tooland/or negative pressure in the lower part of the mould tool.

The process is terminated when the film has cooled to a “stable”temperature range in which it is no longer deformable.

Then the moulding station opens and with the removal of the mouldedcavities the next section of the film is introduced into the mouldingstation.

Due to a possible cycle lengthened by the sealing station, there may bewaiting periods, for example during cooling of the film in the lowerpart of the mould tool and/or on opening the moulding station.

In the following, an advantageous embodiment of the disclosure isexplained in more detail with reference to the below drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic side view of a packaging machine according to thedisclosure in the form of a deep-draw packaging machine;

FIG. 2 is a schematic vertical section through the moulding station withpreheating station of the packaging machine shown in FIG. 1 in openedposition;

FIG. 3 a is a schematic view of the moulding station shown in FIG. 2 inclosed position with the moulding process starting;

FIG. 3 b is a schematic view of the moulding station shown in FIG. 2 inclosed position during the moulding process;

FIG. 3 c is a schematic view of the moulding station shown in FIG. 2 inclosed position with the moulding process finished;

FIG. 3 d is a schematic view of the moulding station shown in FIG. 2 inopen position and with the moulding process finished;

FIG. 4 a is a schematic plan view of the film, the heater elements andthe various heating regions;

FIG. 4 b is a graphical representation of the temperature distributionin the film in section IV-IV in FIG. 4 a;

FIG. 5 is a schematic view of the moulding station shown in FIG. 2 inclosed position in a variant with heater elements in the mouldingcavity; and

FIG. 6 is a schematic view of the moulding station shown in FIG. 2 inclosed position in a variant with heater elements on a stamp.

DETAILED DESCRIPTION

In the figures identical components are designated with the samereference numerals throughout.

FIG. 1 shows a schematic view of a packaging machine 1 according to thedisclosure in the form of a deep-draw packaging machine. This deep-drawpackaging machine 1 has a moulding station 2, a sealing station 3, atransverse cutting device 4 and a longitudinal cutting device 5 whichare arranged in this order in the working direction R on a machine frame6. At the input end on the machine frame 6 there is a feed roll 7 fromwhich a film 8 is pulled off. In the region of the sealing station 3 amaterial store 9 is provided from which a lid film 10 is pulled off. Atthe output end on the packaging machine a removal device 13 in the formof a conveyor belt is provided with which finished, singled-out packagescan be taken away. Furthermore, the packaging machine 1 has a feeddevice, which is not shown and which grips the film 8 to transport itfurther in the working direction R during each main operating cycle. Thefeed device can, for example, be realised using transport chainsarranged on both sides.

In the illustrated embodiment the moulding station 2 is formed as adeep-drawing station with which cavities 14 can be formed in the film 8by deep drawing. Here, the moulding station 2 can be formed such thatseveral cavities can be formed adjacent to one another in the directionperpendicular to the working direction R. In the working direction Rbehind the moulding station 2 an insertion section 15 is provided inwhich the cavities 14 formed in the film 8 are filled with the product16.

The sealing station 3 has a closable chamber 17 in which the atmospherein the cavities 14 can be replaced, for example, by gas flushing with areplacement gas or with a gas mixture before sealing.

The transverse cutting device 4 is formed as a punch which parts thefilm 8 and the lid film 10 in a direction transverse to the workingdirection R between adjacent cavities 14. Here, the transverse cuttingdevice 4 operates such that the film 8 is not parted over the completewidth, but rather is not parted at least in a marginal region. Thisfacilitates controlled further transport by the feed device.

In the illustrated embodiment the longitudinal cutting device 5 isformed as a cutter arrangement with which the film 8 and the lid film 10are parted between adjacent cavities 14 and on the side edge of the film8 so that singled-out packages are available behind the longitudinalcutting device 5.

The packaging machine 1 also has a controller 18. It has the task ofcontrolling and monitoring the processes running in the packagingmachine 1. A display device 19 with the operating elements 20 is usedfor visualising or influencing the process sequences in the packagingmachine 1 for, respectively by, an operator.

The general principle of operation of the packaging machine 1 is brieflydescribed in the following.

The film 8 is pulled off the feed roll 7 and transported through thefeed device into the moulding station 2. In the moulding station 2cavities 14 are formed in the film 8 by deep drawing. The cavities 14are transported further together with the surrounding region of the film8 in a main operating cycle to the insertion section 15 in which theyare filled with the product 16.

Then the filled cavities 14 are transported into the sealing station 3by the feed device in the main operating cycle together with thesurrounding region of the film 8. The lid film 10 is transported furtherwith the feeding movement of the film 8 after a process of sealing ontothe film 8. Here the lid film 10 is pulled from the material store 9. Bysealing the lid film 10 onto the cavities 14 closed packages are createdwhich are transported singled-out into the following cutting processes 4and 5 and transported out of the packaging machine by means of theremoval device 13.

FIG. 2 illustrates a moulding station 2 with a preceding preheatingstation 21 in a variant with a preheater 22 arranged above and also apreheater 23 arranged below. This configuration is practicable primarilywith thick films 8, because the time duration for the heating of thefilm 8 only in the moulding station 2 is so large that the resultingtime of an operational cycle can extend unnecessarily and thus thecapacity of the packaging machine 1 can be reduced in terms of theproduction of packages per minute.

The moulding station 2 comprises a lower part of the mould tool 24 withthe moulding cavities 25. The lower part of the mould tool 24 isimplemented for movement upwards and downwards via a lifting gear whichis not illustrated. Furthermore, the moulding station 2 comprises anupper part of the mould tool 26 in which a heating plate 27 is fitted tothe underside. On the heating plate 27 a plurality of uniformlydistributed heater elements 28 are arranged, implemented as thick-filmheating. The individual heater elements 28 can be controlled via thecontroller 18, and the visualisation or the adaptation of the individualtemperature levels of the heater elements 28 can be realised via thedisplay device 19.

The heating of the film 8 can occur with the moulding station 2 stillopen, during the closing process or only when the moulding station 2 isclosed.

In FIG. 3 a the lower part of the mould tool 24 has been moved up andnow forms a closed chamber 17 with the upper part of the mould tool 26.At the same time the film 8 is clamped all around at the edge by meansof a seal 11 and by the lower part of the mould tool 24 and the upperpart of the mould tool 26 and is tightly closed. Once the film 8 hasbeen heated individually to the desired temperature by means of theindividual heater elements 28, the controller 18 switches the heaterelements 28 off and the moulding process starts in the form of deepdrawing by overpressure above the film 8 and/or negative pressure belowthe film 8. Here, the film 8 initially forms a type of sack due to thepressure difference and the forces acting uniformly on the film 8.

In FIG. 3 b the film 8 has reached the bottom 29 of the moulding cavity25 and also contacts the moulding cavity 25 in the upper region of theside walls 30. These surfaces have a very much lower temperature thanthe film 8 so that here the film 8 is cooled. In order that the film 8does not cool down below the temperature for the plastic deformation inthe moulding time remaining, these regions 29 and 30 of the film 8 areheated to a higher temperature level than the other regions.

In the further course of the moulding process the film 8 is extendedfurther until the film 8 lies completely in the moulding cavity 25, asillustrated in FIG. 3 c. When the film 8 has cooled down so much thatthe moulded cavity 14 is stable, the moulding station 2 opens with thelower part of the mould tool 24 moving downwards, as illustrated in FIG.3 d.

In the plan view FIG. 4 a shows the heating surface of the heating plate27 with grid or matrix shaped, closely contacting heater elements 28 andfour regions 31 to 34. The graph in FIG. 4 b shows the four differenttemperature levels 31′ to 34′ distributed over the heating surface,which arise due to the different temperatures of the heater elements 28in the regions 31 to 34.

In FIG. 5 a variant of the packaging machine 1 according to the presentdisclosure is shown in which, in addition to the heating surface on theupper part of the mould tool 26, further heating surfaces 35 and 36 arefitted to the walls and bottom of the moulding cavity 25.

As another variant, an embodiment of stamp deformation is illustrated inFIG. 6. On the stamp 37 the surfaces which are in contact with the film8 have heater elements 28 fitted which ensure individual temperaturelevels in these regions.

The heating surfaces of the packaging machine according to the inventionare not restricted to the illustrated embodiments, but rather othercombinations or regions can be implemented in the moulding station withheater elements.

For controlling individual temperature levels it is also conceivablethat with many small heater elements 28 they are not all controlledindividually, but rather in groups by the controller 18.

The film 8 can comprise a plastic film, another thermoformable materialor a combination of materials.

The packaging machine 1 according to the invention also comprises amoulding station 2 for a lid film in order to individually heat it anddeform it before sealing with the film 8.

While embodiments of the invention have been illustrated and described,it is not intended that these embodiments illustrate and describe allpossible forms of the invention. Rather, the words used in thespecification are words of description rather than limitation, and it isunderstood that various changes may be made without departing from thespirit and scope of the invention.

What is claimed is:
 1. A packaging machine comprising: a mouldingstation having at least one heating surface with a plurality of heaterelements per heating surface; and a controller configured toindividually control the heater elements in order to bring differentregions of a film to different temperature levels; wherein the heaterelements are formed as thick-film heater elements.
 2. A packagingmachine according to claim 1 wherein the at least one heating surface isconfigured as a heating plate, a stamp and/or surfaces of a mouldingcavity.
 3. A packaging machine according to claim 1 wherein the heaterelements are integrated into a common heating plate or heating mat.
 4. Apackaging machine according to claim 1 wherein that at least one heatingsurface comprises two mutually facing heating surfaces, and wherein theheater elements arranged on one heating surface are mirrored with theheater elements on the other heating surface.
 5. A packaging machineaccording to claim 1 wherein the at least one heating surface comprisesa plurality of heating surfaces that can be heated independently of oneanother.
 6. A packaging machine according to claim 1 wherein themoulding station is configured to perform a moulding process on thefilm, and wherein the at least one heating surface is coolable duringthe moulding process.
 7. A packaging machine according to claim 1wherein the packaging machine is implemented as a deep-draw packagingmachine with an intermittent operational cycle.
 8. A packaging machineaccording to claim 1 wherein the film is a plastic film.
 9. A method foran intermittently operating a deep-draw packaging machine with amoulding station, the method comprising: feeding a film into themoulding station, wherein the moulding station comprises at least oneheating surface with a plurality of heater elements formed as thick-filmheater elements, wherein the heater elements are controllableindividually by a controller in order to heat the film to differenttemperature levels; closing the moulding station to create a tightlyclosed chamber; controlling the heater elements with the controller fora spatially inhomogeneous temperature distribution in the film;positioning the film on the heater elements; switching off the heaterelements after reaching the different temperature levels in the film;deforming the film in a mould tool part of the moulding station; coolingthe film in a stable and no longer plastically deformable temperaturerange; opening the moulding station; and removing the deformed film fromthe moulding station.
 10. A method according to claim 9 wherein the atleast one heating surface comprises at least two mutually facing heatingsurfaces on which the heater elements are in each case mirrored withrespect to one another, wherein in each case two mutually facing heaterelements are operated together on the oppositely situated heatingsurfaces.
 11. A method according to 9 wherein the at least one heatingsurface comprises a plurality of heating surfaces, of which at a pointin time only one is heated at least progressively.